The present invention relates generally to satellite communications and, more specifically, to a beyond line of sight (BLOS) communication system in which mobile terminals can experience channel blockage events.
Developments in broadband beyond line of sight communications have focused mainly on ground-mobile platforms and, to a lesser extent, on maritime vessels and fixed wing aircraft. For example, in recent years, there have been advances in precision tracking antenna technology. Some progress has also been made in the area of waveform construction and protocol performance for the ground-mobile environment.
Advances relating to rotary-wing aircraft and other platforms that experience occlusions have been conspicuously absent. Helicopter communications, for example, can experience periodic outages such as when the rotor blades block the antenna, or when the orientation of the aircraft changes relative to a communications satellite. Rail communications may experience interruptions due to trellises or other overhead structures.
As a result, these platforms have been relegated to relatively low data rate systems such as UHF SATCOM (Ultra High Frequency Satellite Communications) and Inmarsat's L-band GAN (Global Access Network) service. Conventional systems such as these can only offer data rates of between 64-384 kbps and have thus failed to keep pace with the rapidly increasing demand for bandwidth required to support modem user applications.